At dusk snowy egrets take over the trees, wild boar grunt through the underbrush and mosquitoes hum off the water as deer pause for a drink.

Despite the sound of hundreds of tourists sipping their evening beers almost within gunshot range, Spain's Coto Donana, a swampy quarter-of-a-million acres emptying into the Atlantic and Europe's biggest natural bird refuge, may yet survive.

After allowing years of ecological abuse, the government is finally acting to protect the Coto, its moving sand dunes, spotted lynx and Spanish imperial eagle, 50 miles south of Seville in southern Spain.

Philip IV, "the hunting king," bagged game while meeting with his cabinet in the Coto in the 16th century. And dictator Gen. Francisco Franco, who routinely brought home 2,000 partridges from a weekend hunt, had only one question when he visited the Coto in 1952 and observed an abundance of water-sucking eucalyptus trees. "Are they damaging the hunting?" he asked.

The government of former Premier Adolfo Suarez, after wrestling with the more urgent problem of leading Spain to democracy after 40 years of Franco dictatorship, decided to move to guard one of the country's natural wonders by doubling the size of the 90,000-acre national park.

Included in the government program are buffer zones for visitors, artificial lakes and tightened regulations on poaching and tourist development. But with builders already holding a four-mile beach strip along the edge of the Coto to construct an expected 30 hotels and 5,000 chalets for 70,000 sea-loving residents, the job will not be easy.

Nearby towns also threaten the Coto by clamoring for a highway through the heart of the reserve, dumping pesticides into the swamp's rivers, mining pyrite and planting eucalyptus trees for quick lumber revenue.

"Every day that passes makes the situation in the Coto more difficult," says Francisco Garcia Novo, ecology professor at Seville University.

"We are like kamikaze pilots," complains government environment director Daniel de Linoa Ortiz. "The government does not have an environment policy. We have to create one."

Parliament sources predicted it could take some time to get the government's program approved and even longer to negotiate the purchase of the land, nearly all in private hands, even though the Coto was declared a national park in 1969.